<?php
//dezend by http://www.yunlu99.com/ QQ:270656184
defined('BASEPATH') || exit('No direct script access allowed');
class CI_Session_memcached_driver extends CI_Session_driver implements SessionHandlerInterface
{
	/**
	 * Memcached instance
	 *
	 * @var	Memcached
	 */
	protected $_memcached;
	/**
	 * Key prefix
	 *
	 * @var	string
	 */
	protected $_key_prefix = 'ci_session:';
	/**
	 * Lock key
	 *
	 * @var	string
	 */
	protected $_lock_key;

	public function __construct(&$params)
	{
		parent::__construct($params);

		if (empty($this->_config['save_path'])) {
			log_message('error', 'Session: No Memcached save path configured.');
		}

		if ($this->_config['match_ip'] === true) {
			$this->_key_prefix .= $_SERVER['REMOTE_ADDR'] . ':';
		}
	}

	public function open($save_path, $name)
	{
		$this->_memcached = new Memcached();
		$this->_memcached->setOption(Memcached::OPT_BINARY_PROTOCOL, true);
		$server_list = array();

		foreach ($this->_memcached->getServerList() as $server) {
			$server_list[] = $server['host'] . ':' . $server['port'];
		}

		if (!preg_match_all('#,?([^,:]+)\\:(\\d{1,5})(?:\\:(\\d+))?#', $this->_config['save_path'], $matches, PREG_SET_ORDER)) {
			$this->_memcached = NULL;
			log_message('error', 'Session: Invalid Memcached save path format: ' . $this->_config['save_path']);
			return $this->_fail();
		}

		foreach ($matches as $match) {
			if (in_array($match[1] . ':' . $match[2], $server_list, true)) {
				log_message('debug', 'Session: Memcached server pool already has ' . $match[1] . ':' . $match[2]);
				continue;
			}

			if (!$this->_memcached->addServer($match[1], $match[2], isset($match[3]) ? $match[3] : 0)) {
				log_message('error', 'Could not add ' . $match[1] . ':' . $match[2] . ' to Memcached server pool.');
			}
			else {
				$server_list[] = $match[1] . ':' . $match[2];
			}
		}

		if (empty($server_list)) {
			log_message('error', 'Session: Memcached server pool is empty.');
			return $this->_fail();
		}

		return $this->_success;
	}

	public function read($session_id)
	{
		if (isset($this->_memcached) && $this->_get_lock($session_id)) {
			$this->_session_id = $session_id;
			$session_data = (string) $this->_memcached->get($this->_key_prefix . $session_id);
			$this->_fingerprint = md5($session_data);
			return $session_data;
		}

		return $this->_fail();
	}

	public function write($session_id, $session_data)
	{
		if (!(isset($this->_memcached) && isset($this->_lock_key))) {
			return $this->_fail();
		}
		else if ($session_id !== $this->_session_id) {
			if (!$this->_release_lock() || !$this->_get_lock($session_id)) {
				return $this->_fail();
			}

			$this->_fingerprint = md5('');
			$this->_session_id = $session_id;
		}

		$key = $this->_key_prefix . $session_id;
		$this->_memcached->replace($this->_lock_key, time(), 300);

		if ($this->_fingerprint !== ($fingerprint = md5($session_data))) {
			if ($this->_memcached->set($key, $session_data, $this->_config['expiration'])) {
				$this->_fingerprint = $fingerprint;
				return $this->_success;
			}

			return $this->_fail();
		}
		else {
			if ($this->_memcached->touch($key, $this->_config['expiration']) || (($this->_memcached->getResultCode() === Memcached::RES_NOTFOUND) && $this->_memcached->set($key, $session_data, $this->_config['expiration']))) {
				return $this->_success;
			}
		}

		return $this->_fail();
	}

	public function close()
	{
		if (isset($this->_memcached)) {
			$this->_release_lock();

			if (!$this->_memcached->quit()) {
				return $this->_fail();
			}

			$this->_memcached = NULL;
			return $this->_success;
		}

		return $this->_fail();
	}

	public function destroy($session_id)
	{
		if (isset($this->_memcached) && isset($this->_lock_key)) {
			$this->_memcached->delete($this->_key_prefix . $session_id);
			$this->_cookie_destroy();
			return $this->_success;
		}

		return $this->_fail();
	}

	public function gc($maxlifetime)
	{
		return $this->_success;
	}

	protected function _get_lock($session_id)
	{
		if ($this->_lock_key === ($this->_key_prefix . $session_id . ':lock')) {
			if (!$this->_memcached->replace($this->_lock_key, time(), 300)) {
				return $this->_memcached->getResultCode() === Memcached::RES_NOTFOUND ? $this->_memcached->set($this->_lock_key, time(), 300) : false;
			}
		}

		$lock_key = $this->_key_prefix . $session_id . ':lock';
		$attempt = 0;

		do {
			if ($this->_memcached->get($lock_key)) {
				sleep(1);
				continue;
			}

			if (!$this->_memcached->set($lock_key, time(), 300)) {
				log_message('error', 'Session: Error while trying to obtain lock for ' . $this->_key_prefix . $session_id);
				return false;
			}

			$this->_lock_key = $lock_key;
			break;
		} while (++$attempt < 30);

		if ($attempt === 30) {
			log_message('error', 'Session: Unable to obtain lock for ' . $this->_key_prefix . $session_id . ' after 30 attempts, aborting.');
			return false;
		}

		$this->_lock = true;
		return true;
	}

	protected function _release_lock()
	{
		if (isset($this->_memcached) && isset($this->_lock_key) && $this->_lock) {
			if (!$this->_memcached->delete($this->_lock_key) && ($this->_memcached->getResultCode() !== Memcached::RES_NOTFOUND)) {
				log_message('error', 'Session: Error while trying to free lock for ' . $this->_lock_key);
				return false;
			}

			$this->_lock_key = NULL;
			$this->_lock = false;
		}

		return true;
	}
}

?>
